the largest castle in the Loire valley. Poenari Castle, elevated on a clifftop 440 m over the river Argeș in Romania. Used as Vlad the Impaler's fortress. Château de Montségur in France was used by the Cathars and lies on the spur of a mountain. Cefnllys Castle in Wales, is a series of 2 castles in Wales. See also Castle Hill castle Hillside castle Hilltop castle Ridge castle References Castles by type